Methods exist for gross characterization of subsurface features of the earth. For example, seismic imaging may be used to map underground features. Seismic imaging systems typically include a transmitter and a plurality of receivers each placed at a different location wherein the receivers are separated in distance from the transmitter. Seismic imaging provides gross characterization that may be unsuitable for applications wherein information regarding features of increased specificity is desired.
RADAR systems are sometimes used for gross characterization of subsurface features of the earth. However, these systems tend to perform poorly in moist conditions and generally provide only gross characterization of subsurface features.
Orbital vibrators are also used for subsurface characterization. These systems may be effective at identifying the compositions of portions of the earth, but are generally not designed to identify anomalous subsurface features of the earth.